The ultrasound system in your lab has a transducer with a small footprint. This kind of transducer has the following disadvantage?

• A. It cannot be focused in the elevational direction
• B. The field of view in the far field is only one-quarter the diameter of the transducer
• C. The near-field lateral resolution is poor
• D. Resolution is degraded at large distances

Answer: (D)

A transducer with a small footprint has a smaller aperture, which causes more beam diffraction. When the aperture is small, the ultrasound beam spreads out more as it travels, so the beamwidth increases with depth. That wider beam means two closely spaced reflectors become harder to separate at greater distances, leading to poorer lateral resolution far from the transducer. So the main disadvantage is that resolution gets degraded at large distances. The other statements aren’t universally true for a small footprint: elevational focusing can still be achieved with appropriate design, the far-field field of view isn’t fixed to a simple fraction of the diameter, and near-field lateral resolution isn’t inherently poor—the issue is the depth-dependent beam spreading that worsens resolution as distance grows.